Solar power has been recognized as a potential primary source of electrical energy. The benefits of using solar power satellites for generating electrical energy which is beamed to the earth by microwave have also been recognized. These benefits include the avoidance of absorption of solar energy by the atmosphere, obscuration by clouds or dust and avoidance of atmospheric effects on the solar power structure. Further, solar power satellites avoid the limited availability of the sun's radiation at low sun angles and the lack of any solar energy at night. By avoiding these interruptions in solar energy associated with earth based units, solar power satellites eliminate the need for standby storage units normally required in earth based solar cell assemblies. Satellite based solar power units also permit the construction of units of sufficient size, normally on the order of many square miles, necessary to produce electric power at a capacity which make such a project economically feasible.
Several satellite based units have been proposed. For example, such a unit is disclosed in U.S. Pat. No. 3,781,647, issued Dec. 25, 1973, to Peter E. Glaser. Such units have normally required active cooling systems which have made the systems uneconomical. Further, although primary and secondary reflective configurations used in conjunction with solar cells have been proposed in land based solar cell units, such as shown in U.S. Pat. No. 3,419,434, issued Dec. 31, 1968 to E. W. Colehower, such configurations have not provided an optimum solar assembly readily adaptable to satellite based units. U.S. Pat. No. 4,131,485, issued Dec. 25, 1978 to Meinel et al also discloses a solar cell unit employing a primary and secondary reflector arrangement. However, this unit fails to provide an optimum arrangement.
In solar power satellites, solar cells represent approximately 50-80% of the satellite cost at concentration ratios of two. Thus, a cost reduction is achieved if sunlight can be concentrated with low cost reflectors. Additionally, in solar power satellites, solar cells must be properly cooled to maintain a high efficiency. Effective radiation cooing provides a significant cost and weight savings over active cooling systems which require heat exchange fluid and the associated pumps and other structure needed to operate active cooling systems.
Further, an effective solar power satellite must provide a low cost method to fabricate and control the reflector, none of which is now provided by the prior art.